t4nk147

function nth(list, n) {
  if (!list)
    return undefined;
  else if (n == 0)
    return list.value;
  else
    return nth(list.rest, n - 1);
  }
undefined

someList = {value: 5 rest:{value: 10, rest:{value: 20, rest: null}}}

nth(someList, 2);  //=> 20